Wing Thing had its second outing today, with two successful flights of over 15 minutes each. I really need to find a way of flying and photographing it at the same time, as it has such an iconic shape in the air. The first launch with the 7×3 Graupner folding prop was a bit of a disaster, with too little power it just hit the ground. The propeller was over-revving as the ESC was skipping with the throttle at 100%. Switching back to the 8×4.5 Graupner folding prop was a massive improvement, resulting in more power, throttle usable over the full range and a 15 minute flight. With this CG position (full forward), the aircraft was very nose-heavy and I was having to hold about 20% elevator to stay level. I had to make one aborted approach to land due to too much speed, but the actual landing was fine, if a little fast. This airframe’s drag is obviously very low as it moves deceptively fast through the air. Landing is tricky because of the speed and the fact that, as the speed comes off, the elevator loses effectiveness and becomes just an air brake. There doesn’t seem to be any way to float the aircraft in, you just have to run it along the ground almost flat.
The second flight was similar, but the CG was moved back 10mm by moving the LiPo. This resulted in a reduced nose heavy feel, with power on balance having zero pitch down but, turn the power off, and the nose drops rapidly. This is great for launching, which was scaring the life out of me, as this time it flew away from my hand without me having to grab the elevator. My impression is that the CG can go back a bit more, but the wing incidence needs to be increased to reduce the thrust/wing incidence angle for the power off trim to match the power on.
I’ve just finished recharging the first LiPo pack and it’s put 612mAh back into a 1300mAh 3S pack (to 80% storage), which was showing voltages of 3.8v at the start, so it looks like 15 minutes is about the flight time to expect. This was with me saving the power and gliding (badly) for parts of the flight. Interestingly, the second pack only put back about half that after recharge, so I obviously didn’t take as much out of that pack.
In addition to the wing I also flew my HubSan Q4 quad as the new batteries arrived from RobotBirds earlier in the week. I was hoping to fly the X4 as well, but the new batteries for that haven’t fixed the power problems I’ve been having. The X4 just doesn’t want to power on. I’ve tested the voltage all around the circuit, so it’s not something simple like a broken connection. I’m going to have to open this up and have a closer look later.
I also managed to fly a ParkZone Radian which was quite eventful. The aircraft seemed very good until I got some distance from myself about two minutes into the flight and lost control completely. The first indication was the rudder not turning the aircraft, followed by the realisation that I had no control at all. This is unusual with modern radio sets as the range was probably only about 30-40 metres. It really wasn’t that far away and was still quite low, so the Planet 9 radio should have still worked even if it was only a park-fly receiver. In the event, the power off and slight up failsafe setting resulted in about four or five stalls with the aircraft circling around the same position, so I was happy to let it come into range again. Once I had it under control again, I flipped it into wind scrubbed off all the height and speed and brought it down as quickly as possible. Further investigation of the receiver aerial suggests it might have been twisted, but future flights will use a better receiver.
Finally, I also watched an F22 made from Depron card fly exceptionally well, plus a Mustang made from the same materials fly not so well. And I nearly forgot some HLGs that turned up part way through the morning.
Wing Thing Post Flight Test Data:
Measured with 8×4.5, 1300mAh 3S LiPo: 11.7 amps, 133 watts, 10,620 RPM
Stated no load RPM for a Typhoon Micro 6/3D is 10,800 RPM, so my RPM figure looks rather high (98%). Also, max power is stated at 90W, but the suggested prop for a 3S is 8×3.8, so I must be in the right area. Most of the flight only used 50% throttle anyway.